This invention relates to the field of electrical power conversion, particularly to semiconductor switch drivers required to provide a low power consumption.
Most contemporary power switching converters contain one or more power switching devices. In high power applications, a gate driving circuit is used to drive the switches on and off. A typical gate driving circuit is represented in FIG. 1. A controller 10 provides a control signal 12 for a driver 11 which acts as a buffer and provides sufficient turn-on and turn-off currents to drive the switching element Q1 on and off. Further by reference to FIG. 2, from the gate perspective the switching element Q1 may be characterized by an internal resistance Rg and a lumped capacitance Ciss.
An electric charge is provided by the driver 11 to charge the internal capacitance Ciss each time the switching element Q1 is turned on. The stored charge is to be extracted when the switching element Q1 is turned off, and the related energy is dissipated in the internal resistor Rg, an external resistor R1 coupled between the gate electrode and the driver 11, and the output buffer stage of the driver 11.
In some applications, gate drive power consumption is among the foremost causes of power loss, and accordingly is an impediment to the production and implementation of highly efficient power conversion circuits. Therefore, a solution to decrease the driver power consumption is required.
In various conventional high frequency power converters, drivers may be supplied from the power stage to build up a self-oscillating circuit. Other solutions known in the art include auxiliary switching elements, diodes or transformers, which may introduce additional cost and/or complexity to the converter design.
It would be desirable to provide a gate driving circuit for a power converter, having the benefits of decreased power consumption, but without requiring self-oscillating circuitry or the presence of auxiliary circuit components.